How do I simulate "filling water" in Game Engine
Possible duplicate of this post. What you're trying to do is something not currently possible in vanilla Blender at runtime. 

My advise is to fake it with different planes, particles, etc. but you have to learn Python to do this, and it will require a lot of work. Realtime simulations are demanding on your system, so even if you pull off full water simulation in Blender, 99% of everyone with a personal computer won't be able to run it.

So make a plane as your water surface, apply an animated texture to it, and animate the mesh itself. This way you'll at least have a water surface. For the inflow/outflow, make properties stating the water level. Animate this with two keyframes and let it cycle the values between 1 and 0 to make the water rise and fall. Animate some cylinders with the same process as the water surface so it looks like it's pouring out of something. 

Remember, with any and every game, keep your polycount as low as you can. Running a water simulation at runtime will blow your polycount to the roof, and lag, or even crash on most systems. 

Hope this helps.